User device for communicating data and method

ABSTRACT

A user device for transmitting and receiving data to and from an infrastructure equipment via a wireless access interface. The user device is configured to receive an indication from the infrastructure equipment of a location and duration of a temporal response window for receiving response messages, the response messages being received in response to access request messages and the location and duration of the temporal response window having been determined by the infrastructure equipment. The user device is configured to transmit an access request message for requesting access to the wireless access interface to the infrastructure equipment, and to receive a response message in response to the access request message from the infrastructure equipment, wherein the user device is configured to receive the response message in the temporal response window.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/904,577, filed Jan. 12, 2016, which is based on PCT filingPCT/GB2014/052012 filed Jul. 2, 2014, and claims priority to EuropeanPatent Application 13 179 325.9, filed in the European Patent Office onAug. 5, 2013. The entire contents of each of which are incorporatedherein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to user devices for communicating dataand methods of communicating data.

BACKGROUND OF THE DISCLOSURE

Extending mobile communications network coverage and increasing a numberof devices a mobile communications network can serve is an importantaspect of the design and deployment of such networks. Recently, the useof relay nodes and or nodes with reduced functionality compared to aninfrastructure equipment such as for example base stations have beenpromoted as means to achieve both increased coverage by extending therange of base stations, and increased capacity by defining an increasednumber of smaller cells. In a downlink (transmission from base stationto mobile user device) of a communications system, conventional relayingcommonly involves a signal transmitted from a base station beingrepeated by one or more relays of a relay chain until it is received byan intended user device. Similarly, in the uplink (transmission from themobile user device to base station) the user device would transmit asignal to a relay and the signal would be repeated by one or more relaynodes in a relay chain until it is received by the base station. In thisconventional approach, the downlink and uplink signals received andtransmitted by the user device will be transmitted from and received ata same relay and or infrastructure equipment and so the uplink anddownlink may be said to be coupled.

However, more recently decoupled uplink and downlink communicationnetworks have been proposed in order to increase coverage and capacity.Decoupled uplink and downlink operation may occur for example whenuplink only relays are utilised and or uplink and downlink signals aretransmitted from and received at different relay nodes and or differentinfrastructure equipment. For instance, a user device may transmit anuplink signal to a nearby relay but receive its downlink signal directlyfrom a base station, thus the communications paths of the uplink anddownlink signals are different. This scenario can lead to increasedcoverage provided by the base station and may occur due to the greatertransmission power of a base station compared to a user device. Forexample, due to power constraints, a mobile user device may only be ableto transmit to a nearby relay whereas the higher transmission powerassociated with the base station will allow the downlink signal to betransmitted with sufficient power that it can be received directly bythe mobile user device.

Although the use of decoupled uplink and downlink communications mayprovide additional coverage and flexibility to a communications network,a number of problems are presented. For instance, the timing of downlinksignals whose transmission time is defined with respect to atransmission of an associated uplink signal may no longer be able to bereliably known at a user device because of the variable andunpredictable propagation times between the user device and the basestation due to the presence of relays for example. Communications ofthis nature are often termed semi-synchronous communications and therandom access procedure in an LTE network is an example of such asemi-synchronous procedure. In an LTE network a user device may requireuplink resources in order to send a message. If in an unconnected state,the user device may transmit a request for access to the network. In anLTE network, the request for access can be a random access preambletransmitted on a physical random access channel (PRACH). In somenetworks, the user device may transmit the request for access to a relaywhich may pass on the request to a base station or another relay, orindicate to the base station by an alternative means that a request foraccess has been received. The mobile device is configured to wait oncethe request has been sent and attempt to receive a response to therequest during a predefined time period after the transmission of therequest. If a response is not received within this period the mobiledevice may attempt to initiate a subsequent access request procedure.However, due to the variable time for the request to reach the basestation via one or more relay nodes, the response to the request foraccess may not be transmitted by the base station within the predefinedtime period. Consequently, the user device may waste power by attemptingto receive a response to the request when one may not be transmitteduntil some time into the predefined time period and/or before the end ofthe predefined time period and also by unnecessarily initiating asubsequent access request procedure when a response is not receivedbefore the end of the predefined time period.

SUMMARY OF THE DISCLOSURE

According to an example embodiment of the present disclosure, a userdevice for transmitting and receiving data to and from an infrastructureequipment via a wireless access interface is provided. The user deviceis configured to receive an indication from the infrastructure equipmentof a location and duration of a temporal response window for receivingresponse messages, the response messages being received in response toaccess request messages and the location and duration of the temporalresponse window having been determined by the infrastructure equipment.The user device is figured to transmit an access request message forrequesting access to the wireless access interface to the infrastructureequipment, and to receive a response message in response to the accessrequest message from the infrastructure equipment, wherein the userdevice is configured to receive the response message in the temporalresponse window.

The provision of a response window whose timing is determined by theinfrastructure equipment allows the response window to be adapted to thetransmission of the response message when there is a dynamic or cellspecific delay in transmitting the response message. For instance, ifthe time taken for a access request message to reach the infrastructureequipment and be processed at the infrastructure equipment is variableand unpredictable, the infrastructure defined response window enablesthe period of time over which the infrastructure equipment may transmitand a user device may receive a response message to be delayed and orextended to a later end time. This may mean that fewer resources in thedownlink are allocated to the response window(s) compared to a responsewindow which is not delayed but extended to an equivalent end time, andthe user device is not required to be in a receiving mode for anextended continuous window, thus conserving power. Furthermore, thisapproach increases the probability that a response message transmittedby the infrastructure equipment will be received by the user device.Consequently, this will also reduce the probability that additionalaccess request messages will be made by the user device, thus reducinguplink resource requirements and reducing power consumption at the userdevice.

Accordingly to another example embodiment of the present disclosure, theuser device is configured to receive the response message in one or moreof a plurality of temporal response windows, the plurality of responsewindows separated in time, a location and duration of the temporalresponse windows having been determined by the infrastructure equipmentand the user device having received an indication of a location andduration of at least one of the response windows from the infrastructureequipment.

The provision of a plurality of response windows which are determined bythe infrastructure equipment allow the response windows to be adapted tothe transmission of the response message when there is a variable,unknown or cell specific delay in transmitting the response message. Forinstance, if the time taken for a access request message to reach theinfrastructure equipment is variable and unpredictable, the responsewindows enable the period of time over which the infrastructureequipment may transmit a response message and a user device may receivethe response message to be extended in a predetermined way withoutrequiring a continuous extended window or delaying of a single window.This means that fewer resources in the downlink are allocated to theresponse window(s) and the user device is not required to be in areceiving mode for an extended continuous period, thus conserving power.Furthermore, the distribution of the timing of the response windows maytake account of a probability that a response message will be ready tobe transmitted at a certain point in time. This therefore enables theuser device to concentrate its reception efforts on periods where it ismost likely that a response message will be transmitted. Consequently,this will also reduce the probability that additional access requestmessages will be made by the user device, thus reducing uplink resourcerequirements and further reducing power consumption at the user device.

In another example embodiment of the present disclosure, the user deviceis configured to transmit the access request message to theinfrastructure equipment via one or more relay nodes.

The use of relays in the uplink of the communications system allows thecommunications system's coverage to be increased. However, introducingrelays into the uplink can add further unpredictability to the timing ofreceiving an access request message and transmitting a response messageat the infrastructure equipment. The use of a plurality of responsewindows may take account of this increased unpredictability by allowingthe response windows to be adapted to take account of theunpredictability whilst avoiding unnecessary control informationreception and energy consumption the user device.

In another example embodiment of the present disclosure, the indicationof a location and duration of at least one of the response windows isreceived by the user device from the infrastructure equipment prior tothe transmission of the access request message.

Providing an indication of the response windows to the user deviceallows the infrastructure equipment to set cell and user specificresponse windows. These windows may then take account of delaycharacteristics and user device priorities which are specific to theinfrastructure equipment's cell, thus leading to a more efficientoperation of the cell.

In another example embodiment of the present disclosure, the user deviceis configured to enter a reduced power state during the time separatingthe response windows.

Entering a reduced power state during the period between the responsewindows allows the user device to conserve power when it has knowledgethat a response message will not be transmitted by the infrastructureequipment, thus leading to extended battery life at the user device.

In another example embodiment of the present disclosure, the user deviceis configured to receive an indication of a timing of at least one ofthe response windows from the infrastructure equipment in one of theresponse windows.

Allowing an indication of the timing of a response window in a precedingresponse window allows the timing of response windows to be dynamicallycontrolled by the infrastructure equipment. For example, if anunforeseen delay has occurred and a response message is unable to betransmitted in a subsequent response window, this may be indicated tothe user device. This will therefore allow the user device to avoidattempting to receive a response message during the subsequent responsewindow, thus conserving power.

In another example embodiment of the present disclosure, the user devicehas an identifier associated therewith and the infrastructure equipmentis configured to determine the location and duration of at least one ofthe response windows based upon the identifier of the user device and apredetermined rule, and the user device is configured to determine thelocation and duration of the at least one of the response windows basedon the identifier associated therewith and the predetermined rule.

Allocating response windows based on user device's identity allows aplurality of response windows to be allocated among a plurality of userdevices without the requirement of user device specific signallinginformation, thus conserving downlink resources and reducing a quantityof signalling information required to be received the user device.

In another example embodiment of the present disclosure the user deviceis a 3GPP LTE compliant device.

In another example embodiment of the present disclosure the accessrequest message includes a random access preamble and the responsemessage is a random access response

Various further aspects and features of the present disclosure aredefined in the appended claims, including but not limited to, methods ofcommunicating data between a user device and an infrastructureequipment.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample only with reference to the accompanying drawing in which likeparts are provided with corresponding reference numerals and in which

FIG. 1 provides a schematic illustration of a coupled uplink anddownlink relay communications network;

FIG. 2a provides an illustration of a contention based access requestprocedure;

FIG. 2b provides an illustration of non-contention based access requestprocedure;

FIG. 3 provides a schematic illustration of a decoupled uplink anddownlink relay communications network;

FIG. 4 provides an illustration of response windowing in accordance withan embodiment of the present disclosure;

FIG. 5 provides an illustration of response windowing in accordance withan embodiment of the present disclosure;

FIG. 6 provides an illustration of response windowing in accordance withan embodiment of the present disclosure;

FIG. 7 provides an illustration of response windowing in accordance withan embodiment of the present disclosure;

FIG. 8 provides an illustration of response windowing in accordance withan embodiment of the present disclosure;

FIG. 9 provides an illustration of an access request procedure inaccordance with an embodiment of the present disclosure;

FIG. 10 provides an illustration of an access request procedure inaccordance with an embodiment of the present disclosure;

FIG. 11 provides an illustration of an access request procedure inaccordance with an embodiment of the present disclosure; and

FIG. 12 provides an illustration of an access request procedure inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Coupled Communications System Architecture

FIG. 1 provides a schematic illustration of a relay based communicationssystem where the uplink and the downlink communications are coupled suchthat the uplink and downlink signals propagate via the samecommunications network infrastructure. The system comprisesinfrastructure equipment such as for example a control node or basestation 101, one or more user devices or user equipment (UE) 102 and oneor more relays or relay nodes 103, where the base station is arranged toprovide a wireless access interface to the user device and to transmitand receive data to and or from the user device 102 via the wirelessaccess interface. The user device 102 communicates in the uplink bytransmitting a signal via one or more relay nodes 103 to the basestation 101, where the uplink signal path is represented by the arrow104 and the user device may for example be a high data rate mobiledevice such as a smart phone or a lower data rate device such as amachine type communications (MTC) device e.g. a smart meter or medicaldevice. In the downlink, the base station 101 transmits a downlinksignal via one or more relay nodes 103 where the downlink signal path isrepresented by the arrow 105. The system of FIG. 1 may operate inaccordance with any mobile communications network protocol known in theart, for example it may operate in accordance with 3GPP LTE where thebase station may be an enhanced NodeB (eNB). The relay nodes may bededicated relays nodes which repeat a received signal via knownrepeating techniques such as amplify and forward or decode and forward.The relay nodes may also be lower functionality base station or userdevices which are configured to provide relay functionality. The relaynodes may be connected to the base station via a dedicated backhaul linksuch as an X2 link or X2 interface, or any other suitable wired orwireless link such as point to point microwave connection. In exampleswhere the relays are lower functionality base stations or eNBs, therelays may form separate cells such as a pico cells, however, thescheduling tasks and the like may still be performed by the base station101. The uplink and downlink communications over the wireless accessinterface between the base station, relay nodes and user devices takeplace within the framework of uplink and downlink time frames which aredivided into a number of separate physical channels. The system may alsooperate in accordance with time division duplexing, frequency divisionduplexing or any other duplexing or multiple access scheme known in theart. In examples where the network of FIG. 1 operates in accordance withLTE, the user devices 103 will be allocated resources in uplink framesby the base station 101. For example, if the user device is in anunconnected state with the base station and wishes to connect to thebase station, the user device is required to perform a random accessprocedure which acts as request for access to the network.

LTE Random Access Procedure

FIG. 2a illustrates an LTE contention based random access procedure thata user device may perform in order to request access to an LTE network.Firstly, the user device selects a random access preamble from a set ofcontention based random access preambles that has been broadcast in asystem information block (SIB) such as SIB2 in a downlink frame by thebase station. The user device then transmits the selected random accesspreamble 201 to the base station where this transmission acts as anaccess request message for requesting access to the network and thepreamble acts as a user device identifier. The random access preamblemay be transmitted on a physical channel within the wireless accessinterface such as a physical random access channel (PRACH) of an uplinkframe. Once the random access preamble has been received by the basestation, at step 202 the base station transmits a response message, suchas for example, a random access response (RAR). The resources in timeand frequency of a downlink channel, such as a physical downlink sharedchannel (PDSCH), in which the user device can find the RAR are indicatedin a message on a control channel such as physical downlink controlchannel (PDCCH) addressed to a random access radio network temporaryidentifier (RA-RNTI) and which is transmitted in the same subframe asthe response message. This message is therefore required to be receivedprior to receiving the response message. In particular, a downlinkcontrol information (DCI) message informing the user device of theresources where the response message can be found in the currentsubframe is sent on the PDCCH, where the RA-RNTI is formed from a timeand, in some examples, a frequency identifier of transmission of theassociated access request message. The response message contains atleast the identity of the received preamble, a timing alignment command,an allocated uplink resource grant and a temporary Cell RNTI (C-RNTI).Upon receiving the response message, the user device transmits ascheduled transmission containing its intended message, such as a radioresource controller (RRC) connection request, in the allocated uplinkresources as shown by step 203. Finally at step 204, upon receiving theintended message the base station transmits a contention resolutionmessage. The contention resolution message is then acknowledged by theuser device to which the contention resolution message is addressed, forexample with a HARQ ACK/NACK. This procedure thus overcomes thepossibility of multiple user devices utilising the same preamble and ortransmitting a random access request over the same channel at the sametime.

FIG. 2b illustrates an example non-contention based random accessprocedure for requesting resources in an LTE network. At step 251, priorto the transmission of a random access preamble from the user device inthe access request message, the base station allocates a preamble from anon-contention based set of preambles to the user device. Thisallocation may be performed via a format 1A downlink control information(DCI) message on the PDCCH or in a handover command if the user devicehas recently entered a cell served by the base station. At step 252 theuser device transmits its allocated preamble to the base station. Oncethe preamble has been received at the base station, the base stationtransmits a response message, such as for example a random accessresponse, at step 253 where the response message contains similarinformation to the response message sent at step 202 of FIG. 2a . Oncethe response message has been received at the user device, the userdevice then transmits its intended message in the allocated uplinkresources indicated in the response message.

Although the access request procedures of FIGS. 2a and 2b has beendescribed with reference to sending a receiving messages directly from abase station, the messages may also be sent and received via one or morerelays using the same procedure. For example, the messages may be sentand received via the communications paths illustrated in FIG. 1, wherein the uplink a receiving relay either relays a message to another relayor a base station, and in the downlink relays the message to anotherrelay or a user device.

Response Windowing

Both access request procedures described above are reliant on receptionof a response message at the user device. In an LTE system the responsemessage is transmitted on a physical downlink shared channel (PDSCH) andis scheduled by information on a physical control channel such as aPDCCH. In systems such as LTE, in order to ensure that a user devicedoes not attempt to receive a response message continuously from thepoint in time of the transmission of the access request message until aresponse is received, the response message is transmitted by the basestation in a predetermined temporal response message window. In LTE,when the access request message is a random access request and theresponse message is a random access response, such a window may bereferred to as a random access response window or a RAR window. Aresponse window may reduce the amount of power consumed at the userdevice because a finite time period during which the user device willattempt to receive a response message is defined. The response window isdefined with respect to the transmission of the access request message,such as three subframes after transmission in LTE, and the user deviceis configured to begin to attempt to receive the response message whenthe response window commences. In an LTE system the process of receivinga response message includes the user device checking the PDCCH of eachsubframe within the response window for a relevant DCI containing PDSCHscheduling information addressed to its RA-RNTI. When such schedulinginformation is found, the user device receives and decodes the responsemessage in the PDSCH of the corresponding subframe, where the responsemessage contains an indication of the preamble the user device sent tothe base station in the access request message. Once a response messageis successfully received the user devices ceases to check the PDCCH forresponse message scheduling information. If a response message is notreceived by a user device within the response window, after a minimumwait period the user device begins a subsequent new access requestprocedure, where the subsequent access request procedure is similar tothose previously described with reference to FIGS. 2a and 2b . Multipleresponse messages for different user devices may be transmitted by thebase station within each response window therefore reducing congestion.If multiple response messages are present in a single response windowthe user devices may differentiate between them by means of the RA-RNTIto which they are addressed and the preamble they each contain.

An access request procedure such as that described above may be referredto as being semi-synchronous with the user device preamble transmission.This is as a result of the response window being defined with respect tothe subframe containing the end of the user device preambletransmission. This is opposed to the response window being directlydefined with regards to a downlink subframe. More specifically, in LTEsystems the response window commences three subframes after the subframecontaining the end of the user device preamble transmission and has alength indicated in the SIB2 block in which the preamble configurationis broadcast. According to 3GPP LTE Release 11 specifications, theduration of the response window may be at least one subframe for thecontention based random access procedure and at least two subframes forthe non-contention based random access procedure. However, these windowsmay not be longer than 10 subframes. The response window lengths andstructure specified for LTE are suitable for coupled uplink and downlinkLTE system such as that illustrated in FIG. 1 and non-relay basedsystems where the latency of communications between a user device and abase station are consistent and predictable and there beginning of theresponse window can be fixed. However, the length, location andstructure of the response window may not be suitable where latency incommunications between the user device and the base station are neitherconsistent not predictable.

Decoupled Communications System Architecture

FIG. 3 provides a schematic diagram of a second example communicationsnetwork. The networks of FIG. 1 and FIG. 3 are substantially similar,however, the uplink and downlink of the network of FIG. 3 are decoupled.In FIG. 3 decoupling refers to the different nodes which the user devicetransmits data to and receives data from, for example the user devicetransmits data to a relay node but receives data directly from thecontrol node or infrastructure equipment 101 In this example, thesecommunications paths may arise because the relay nodes are uplink onlyrelays and therefore unable to participate in the downlink. A situationas illustrated in FIG. 3 may also arise without the presence of uplinkonly relays when a base station transmits at a significantly higherpower than a user device. In such a scenario, the downlink signal mayhave sufficient power to reach the user device directly but the userdevice may only be able to transmit at a power sufficient to reach anearby relay node which then relays the uplink signal to the basestation. The aforementioned definition of decoupling is from the userdevice's perspective, however, a more general definition may be todefine decoupling as when the communications paths of the uplink anddown link are different i.e. the relays and/or the infrastructureequipment involved in the uplink and downlink communications pathsdiffer. An advantage of uncoupled communications is that coverageprovided by a base station may be increased because a greater number ofuser devices may be able to connect to a base station even though theycannot directly communicate with the base station.

Semi-synchronous access request procedures such as those described withreference to FIGS. 2a and 2b may also be used in conjunction with thecommunication network arrangement of FIG. 3. However, a number ofproblems may result due to the decoupled nature of the uplink anddownlink communications and the fixed response window timing.

The propagation time of an uplink access request message from the userdevice to the base station may be variable due to the latency associatedwith the communications interfaces between the relay nodes and the basestation. In some circumstances, these delays may result in the basestation being unable to transmit the response message within a responsewindow as described above. This may in turn lead to the user devicewhich transmitted the access request message expending power attemptingto receive a response message within the response window when it isunlikely that one will be transmitted. For the case of delay tolerantuser devices such as for example MTC devices, a delay in performing anaccess request procedure in itself is not critical. However, thesedevices are commonly low power devices and therefore the power expendedin an extended access request procedure is a concern. In the case ofuser devices such as smart phones, they may require both a rapid and lowpower access request procedure thus failing to receive a responsemessage is also a concern. Furthermore, in LTE systems if a responsemessage is not received at a user device, the user device may increasethe transmit power of a subsequent access request message and maytherefore expend a comparatively greater amount of power when performinga subsequent access request procedure. These problems may also beexacerbated by the presence of an increased number of relays in theuplink and/or downlink communications path. A number of relays in theuplink communications path may increase unpredictability in thepropagation time of an access request message to the base station. Asimple solution to these problems would be to extend the maximum lengthof the response window so that the probability of a response messagebeing transmitted within the response window is increased. For instance,a maximum response window could be defined according to a maximum delayassociated with the number of relays in the uplink. Although this wouldreduce the probability that a subsequent access request procedure willbe performed by the user device, attempting to receive a responsemessage over an extended window would increase the power consumption ofthe user device. For example, in an LTE system the user device will berequired to receive control information in the PDDCH of each subframe ofthe response window for an indication of the access response message inthe downlink data channel PDSCH. This approach is not an efficient meansto achieve reception of a response message nor does it provide theflexibility that may be required when the latency of communicationsbetween relay nodes and the base station are highly variable andunpredictable due, for example, to congestion on backhaul links.

Although the problems associated with unpredictable response messagetransmissions are present in a decoupled uplink downlink communicationssystem, they may also apply to other network architectures andsemi-synchronous communications procedures. For example, the presence ofat least one relay in the either the uplink or downlink may introducevariability and unpredictability into the reception of access requestmessages at a base station and the subsequent reception of a responsemessages at a user device. This variability and unpredictability, maythus lead to inefficiencies in the reception of semi-synchronous messageresponses i.e. response messages as previously described. Furthermore,in systems where there is a varied processing time associated with asemi-synchronous or synchronous request at the base station it may provedifficult to accurately define an anticipated reception time of a replyto the request without wasting power at the user device due to the useof an extended response window.

Flexible Response Windowing

According to an example embodiment, in a communications system such asan LTE system, a timing of a plurality of temporal response windows aredetermined and indicated to a user device by the base station, where thetiming may include locations in time and durations, both of which may bevariable. The base station is then configured to transmit responsemessages only within a response window. However, in some embodiments oneor more response windows with a variable start time and length may beused and the base station's transmission adjusted accordingly. The userdevice is configured to receive and check a control channel for anindication of a response message only during the response window(s). Forinstance an LTE device may check the PDCCH of subframes during aresponse window for a DCI message addressed to its RA-RNTI, where thePDCCH corresponds to the content of the PDSCH in the subframe. Outsideof the response windows the user device may enter a reduced power statesuch as DRX. FIG. 4 provides a schematic illustration of a responsewindowing pattern or scheme in accordance with this embodiment where anindication of the response windowing may be transmitted within aphysical layer control channel such as a PDCCH in LTE. The responsewindows 401 are separated in time where the time periods between thewindows may be referred to as response gaps 402 and during which theuser device may enter a reduced power state such that it does notreceive or transmit. Response messages are transmitted by the basestation within one of the response windows 401 after the access requestmessage 403 has been transmitted by the user device 102 and received bythe base station 101. Response messages are attempted to be received bya user device within each of the response windows 401. Also in FIG. 4,downlink subframes 404 of a wireless access interface that correspond intime with the response windows are illustrated, where each subframe 404includes a control channel PDCCH 405 and a data channel PDSCH 406 as maybe found in LTE subframes. During the response windows the user devicereceives resource allocation data in the PDDCH 407 transmitted by thebase station. If the presence of a response message is indicated by datareceived across a PDCCH the user device will then receive the relevantdata transmitted across an associated PDSCH. The response windows may besynchronous or non-synchronous with the subframes of the downlink, wherein a synchronous implementation the response windows may commence at thesame time as a PDDCH. However, in either case, if a PDDCH of a subframedoes not fall within a response window the effect is that the PDSCH ofthe subframe is not received by the user device.

This arrangement of response windows allows for extended delays to beaccounted for in the access request procedure without the use of anextended continuous response window, thus reducing a number ofconsecutive PDDCH instances that the user device is required to receivedata from. For example, not all the PDDCH instances between the start ofthe first response window and the end of the last response window arerequired to be received with the aforementioned response windowing. Thisin turn may reduce power consumption at the user device because it canenter a reduced power state during periods when a response message willnot be transmitted such as during the response gaps. In addition tothis, the procedure may also increase the likelihood of receiving aresponse message. For instance, the overall period between transmissionof an access request message and the end of the response window(s) maybe increased compared to a single response window with an equivalenttotal duration. Furthermore, variable duration in time and multipleresponse windows may also reduce the adverse effects on system capacitythat an extended continuous response window may have.

Although the response windows are shown to be of equal duration in timein FIG. 4 they may also be of different durations. Likewise, theresponse gaps may also be of different durations. When implemented inthe previously described relay systems, the user device transmits anaccess request message at 403 and after an initial delay 408 theresponse windowing begins. The response windowing is defined by the basestation and may either be cell specific or user device specific. In thecase of cell specific response windowing, an indication of the timing ofthe response windows in terms of duration and location may be signalled.For instance, in an LTE system response windows may be signalled in asystem information block such as SIB2 by adding an additionalinformation element (IE), or in another signalling resources that a userdevice is capable of receiving prior to transmitting an access requestmessage. In the case of user device specific windowing, in an LTE systemif a non-contention based random access procedure is utilised a devicespecific response windowing could be signalled to a user device alongwith a preamble prior to the random access procedure illustrated in FIG.2 b.

Cell specific response windowing may require less signalling overheadsthan user device specific response windowing but may not provide thesame degree of flexibility. For instance, with user device specificresponse windowing the base station may take account of differentpriorities of different user devices and schedule their response windowsaccordingly. For example, if a particular user device such as a smartphone requires a rapid response to a request for access, the basestation may schedule response windows of a longer duration and closer tothe initial request than for a user device which does not require arapid response, such as smart meter. A situation such as this may occurwhen a high mobility user device is passing through a cell served by abase station and therefore has a high probability of handover. Due tothe possibility that the user device may enter and leave a cell in arelatively short period of time it would be beneficial for an accessrequest procedure for this device to be completed more quickly than fora stationary device within the cell. Examples of prioritisationprocedures may include prioritised scheduling over a communicationsinterface between relay nodes and the base station in order to reduceany latency, and or the prioritisation of processing of the accessrequest message at the base station.

The duration of a plurality of response windows may be signalled by thebase station using an indication of their periodicity, window durationand a total number of windows, the start and end of each response windowindividually, the response gaps, or a combination of these indicators.Each of these indicators may be suited to a different arrangement ofresponse windowing. For instance, individual response windowing may besuited to response windows which are of different durations, whereasindicating the periodicity of the response window may be suited forresponse windowing where the windows are of an equal duration andequally spaced. In some embodiments, signalling of the responsewindowing by the base station may not be required but instead theresponse windowing will be hardcoded into the user device by virtue offor example the specifications of the wireless access interface. Thishardcoded response windowing may act as default response windowing thatmay be overridden or adapted by subsequent signalling. However, in someembodiments it may be the only response windowing available in the cellor to a user device.

In another example embodiment a base station may indicate an initialcell specific response windowing pattern but in a subsequent controlmessage, such as a DCI message in LTE. The control message may betransmitted in a response window where the the base station may indicatein the control message a dynamic configuration of the next responsewindow, thus overriding the initial windowing. For example, in LTE in aresponse window numbered n the base station may transmit a DCI messageindicating the location and duration of the next response windownumbered n+1, or a later response window. In some embodiments a userdevice may cease to attempt to receive a response message in the currentwindow when a dynamic response windowing message is received and enter areduced power mode because it infers that there is to be no responsemessage for it in the current response window. Alternatively, userdevices may continue to attempt to receive a response message in thecurrent response window and if one is received, ignore the n+1 responsewindow. If an updated response window configuration is not received theuser devices may return to using the cell specific response windowingpattern. Dynamic response windowing may be applied to both individualand multiple user devices and also include response windowing which isdependent on the current conditions within the system, such ascommunications latency and processing times at the base station.

The time period 404 represents the initial time period before the startof response windowing and may be signalled in response windowsignalling. However, in some embodiments it may be a common time periodequal to a conventional delay in a fixed response window system i.e.three subframes in an LTE system. An initial time period equal to aconventional delay may be required in order to provide compatibilitywith legacy user devices which utilise a single fixed response window.In other embodiments, in order to further aid compatibility with legacydevices in LTE systems, the total duration of the response windowingincluding the response gaps may be configured to be equal to theconventional single response window duration such that even a responsemessage transmitted in one of a plurality of response windows may bereceived by a legacy device which operates with a single responsewindow.

Outside of the response windows in the response gaps, user devices maybe configured to enter a reduced power state in which they do notattempt to receive downlink and or transmit uplink signals. In LTEdevices, DRX is an example of such a state where in order to reducepower consumption the user device does not attempt to receive somedownlink signals.

Once a user device has received a response message in a response window,it may cease receiving and checking a relevant control channel such as aPDCCH for information on downlink resources. This situation isillustrated in FIG. 5 where downlink subframes 404 that correspond intime with the response widows are illustrated in a similar manner toFIG. 4. In FIG. 5, the user device receives data across PDDCH instance501 but does not receive a response message. However, in PDCCH 502 andPDSCH 503 the response message 504 is sent by the base station 101 andreceived by the user device. Therefore the user device no longerattempts to receive a response message in the remaining response window505 and partial response windows 506. Consequently, the user device doesnot receive data across the PDDCH instances following PDCCH 502.

FIG. 6 provides an illustration of an embodiment of response windowingwhich is similar to that described with reference to FIG. 4 but wherethe duration of the one or more of the response windows is different.Also in FIG. 6, downlink subframes which correspond in time with theresponse windows are shown alongside the response windows as illustratedin FIGS. 4 and 5. This windowing arrangement may be beneficial when theprobability of a response message being transmitted varies over time andtherefore between the response windows. For example, in the system ofFIG. 3, due to propagation delays, processing delays, latency and orcongestion it may be unlikely that a response message will betransmitted by the base station within the first response window 601.Response window 601 has been configured to have a shorter duration.Likewise, there may be an increased probability that a response messagewill be transmitted after point 602 compared to 601 and thereforeresponse window 603 is of an increased duration. Response window 605 isthus the longest duration response window because there is a highestprobability that a response message will be transmitted after point 604.Although in some embodiments a response message may only be transmittedin a response window, the actual response message may have beenprocessed and generated at the base station prior to commencement of anext response window. Consequently, if a response message has beengenerated at a base station it may be buffered or stored in anappropriate memory until the commencement of the next response window.

Punctured Response Windowing

In some embodiments the base station and the user device may beconfigured to perform response window puncturing, where in one responsewindow the base station indicates to the user device that a responsewill not be transmitted in the next response window(s) or until aspecified point in time. FIG. 7 illustrates response windowing inaccordance with such an embodiment, where downlink subframes 404 whichcorrespond in time with the response windows are shown in a similarmanner to FIGS. 4, to 6. During response window 701 the base stationindicates to the user device at 702 via a response window puncturingmessage in PDCCH 703 that a response message will not be transmitted inthe next response window 704 and the remaining period of the currentresponse window 705, or not transmitted until the response window 706.Consequently, the user device may cease attempting to receive dataindicating a response message transmitted across the PDCCH until thecommencement of the response window 706, where it receives data acrossPDCCH 707. Consequently, the user device may enter a reduced power mode,such as DRX, after reception of the response window puncturing messagein PDDCH 703 and until the commencement of the response window 706. Thisprocedure may therefore also include immediately ceasing to attempt toreceive a response message in the current response window 701.Signalling of the response widowing in this embodiment is required to beperformed during a preceding response window so that the user device isnot in a reduced power state and thus able to receive the signalling.For example, in an LTE system the signalling to skip a response windown+1 may take the form of a DCI transmitted during the nth responsewindow. An advantage of placing the response window ‘skip’ message in aresource such as a DCI is that the user device only need decode andreceive data from the PDCCH rather than the PDCCH and the PDSCH, thusreducing power consumption. Furthermore, resources in the PDSCH are nottaken up by the response window signalling and so the associated adverseeffects on the capacity of the PDSCH are avoided. The decision to skip aresponse window by a base station may be based on a number of factorsthat affect the ability of a base station to transmit a responsemessage. For instance, latency and delays on interfaces between relaynodes and the base station, processing delays at the base station,congestion and associated scheduling decisions at the base station,current access request message load such as random access channel (RACH)load in LTE, and any other system condition that the base station mayhave knowledge of.

User Device Dependent Response Windowing

In another embodiment, the response windowing for a user device may bedependent on the identity of the user device. For example, in an LTEsystem a user device's response windowing may be dependent on itsnon-access stratum (NAS) identity such as a system architectureevolution (SAE)-temporary mobile subscriber identity (S-TMSI), randomaccess preamble identifier (RAPID) or if it is RRC_CONNECTED, itsC-RNTI. In a previous embodiment it was described that each user devicemay be allocated an individual response windowing pattern. However, inthis present embodiment the identity of a user device may be used toselect a response windowing pattern from a set of cell specific responsewindowing patterns. FIG. 8 illustrates such an arrangement wheredownlink subframes 404 which correspond in time with the responsewindows are shown in a similar manner to FIGS. 4 to 7. In FIG. 8 each ofthe response windows is numbered from n=1 to n=5 and in one example theallocation of the response windows to user devices may be performed inaccordance with the rule n mod I=k where I is a decimal identityassociated with a user device. For instance, in FIG. 8, if a user devicehas identity I=2 and k=0, the user device will be allocated responsewindows 802 (n=2) and 804 (n=4) and therefore the base station wouldonly transmit a response message intended for this device in responsewindows 802 and 804 and across corresponding PDCCH 806 and PDSCH 807.Accordingly, the user device would therefore attempt to receive aresponse message in the response windows 802 and 804 and acrosscorresponding PDDCH 806 and PDSCH 807. Likewise, if I=5 and k=0 a userdevice and the base station would be configured to transmit and receiverespectively a response message in response window 805. Consequently theuser device would receive control data across PDCCH 808 and theassociated response message across PDSCH 809 if a response message isindicated by the control data. In some embodiments the rule with whichthe window allocation is determined may also be predetermined and knownto user devices such that a user device is able to determine whichwindows it has been allocated based on the rule and its identifier. Thisapproach therefore overcomes the need for window allocations to beindicated to the user device by the infrastructure equipment. Theseembodiments may find application when a large number of responsemessages are required to be sent by the base station due to an eventtriggering many user devices to perform an access request procedure. Insuch a scenario, in order to avoid congestion in the response windows,response window allocation described above may be used to avoidtransmitting every pending response message in each response window.Although in this and previous embodiments it has been described thateach user device may be allocated response window or response windowingpattern, in some embodiments one or more user devices may be allocatedthe same response window or response window pattern and multipleresponse messages sent in them. An approach such as this allowsincreased flexibility in response window allocation thus reducingcongestion, whilst also reducing the required downlink resourcescompared to allocating a unique response window or response windowpattern to each user device.

FIGS. 9 to 12 provide illustrations of example access request procedureswith response windowing which are in accordance with a number of thepreviously described embodiments and implemented in an LTE systems. Inthe LTE system the access request procedure is a random access procedurewhere an access request message is a random access preamble transmissionand a response message is a random access response (RAR). FIGS. 9 and 11illustrate contention based random access procedures with responsewindowing, where a number of the steps are substantially similar tothose of FIG. 2a and only the additional steps are described below.FIGS. 10 and 12 illustrate non-contention based random access procedureswith response windowing where a number of the steps are substantiallysimilar to those of FIG. 2b and only the additional steps are describedbelow.

In FIG. 9 the random access procedure includes the user device receivingdevice specific or cell specific information at step 901 which indicatesthe response windowing, where the response windowing may correspond tothat of FIG. 4. Once the user device has transmitted its access requestmessage at step 201 it is configured to enter a reduced power state andthen exit the reduced power state for each response window 401 until itreceives the response message as a RAR during the third response windowat step 202. Once the RAR has been received the random access procedurecontinues as described with reference to FIG. 2 a.

In FIG. 10 the random access procedure includes the user devicereceiving device specific response windowing information at step 1001,where the response windowing may correspond to that of FIG. 6. Once theuser device has transmitted its access request message at step 252 it isconfigured to enter a reduced power state and then exit the reducedpower state for each response window 601, 603 and 605 until it receivesthe RAR during the third response window 605 at step 253. Once the RARhas been received the random access procedure continues as describedwith reference to FIG. 2 b.

In FIG. 11 the random access procedure now includes receiving cellspecific information indicating the response windowing at step 1101, andsubsequently receiving a secondary indication of response windowing atstep 1102, where the response windowing may correspond to that of FIG.7. Once the user device has transmitted its access request message 201it is configured to enter a reduced power state and then exit thereduced power state for each response window 1103 to 1106. However,during response window 1104 the user device receives a secondaryindication of response windowing at step 1102 which specifies thatresponse window 1105 is punctured i.e. no RAR will be transmitted in thenext response window or the RAR will be transmitted in the nth+2response window. Consequently, the user device may remain in the reducedpower state between response windows 1104 and 1106 and exit for responsewindow 1106 in which it receives the RAR at step 202. Once the RAR hasbeen received the random access procedure continues as described withreference to FIG. 2 a.

In FIG. 12 the random access procedure now includes the user devicereceiving device specific and or cell specific response windowinginformation at step 1201 and subsequently receiving a secondaryindication of response windowing at step 1202. Once the user device hastransmitted its access request message at step 252 it is configured toenter a reduced power state and then to exit the reduced power state foreach response window 1203 to 1205. However, during response window 1204the user device receives a secondary indication of response windowing atstep 1202 which indicates that the next response window 1205 has beenextended in duration to form response window 1206. As a consequence theuser device exits the reduced power mode for an extended periodcorresponding to response window 1206. Once the RAR has been received atstep 253 the random access procedure continues as described withreference to FIG. 2 b.

The above described embodiments allow request procedures such as accessrequest procedures in systems with variable and unpredictable delays,for example those with decoupled uplink and downlink communications, tooperate more efficiently. In particular, user devices that areperforming a request procedure that require a response to be transmittedare no longer dependent on fixed response windows when the transmissionof a response may be unpredictable due to latency and delays betweenrelay nodes and a base station for example. This may result in a reducednumber of unsuccessful request procedures and therefore a reduced numberof request procedures in total. In addition to the power savings at theuser device and in the system as a whole, the reduction in requestprocedures may also lead to reduced interference in a system's wirelessaccess interface. For example, for random access requests in an LTEsystem, interference in physical channels such as the physical uplinkshared channel (PUSCH) and physical uplink control channel and acrosscell edges may be reduced. Furthermore, fewer request procedures willalso utilise fewer resources in the wireless access interface. Forexample, in LTE systems because response messages are transmitted in thePDSCH (with control information in the PDDCH), a reduced number ofaccess request messages will reduce the impact on the capacity of thePDSCH.

Although embodiments have been described with reference to messages forrequesting access and to random access procedures in an LTE system,embodiments may also find application in other semi-synchronous andsynchronous procedures in both LTE systems and other communicationssystem. For example, flexible and control node defined windowing may beapplied to the broadcast and reception of system information in an LTEsystem. In an LTE system SIB2 and higher SIBs are transmittedperiodically over the PDSCH within system information windows(SI-windows). Consequently, if a base station wishes to use the capacityon PDSCH for other data, it may signal to user devices the revisedwindowing in which the SIBs will be transmitted in a manner analogous tothat described above. Furthermore, although the embodiments have beendescribed with reference to particular physical and logical channels ofan LTE system, their operation is not limited to use with thesechannels. The embodiments may be used with any equivalent physical orlogical channels in LTE or other communication architecture, forexample, PDCCH communications may be conveyed on the enhanced PDCCH(EPDCCH) in future releases of LTE or in another form of control channelin an alternative communications system. Likewise, response windowingmay be utilised when no control data specifying resources in a datachannel is transmitted but instead the response in transmitted directlyin the data channel.

Various further aspects and features of the present technique aredefined in the appended claims and various combinations of the featuresof the dependent claims may be made with those of the independent claimsother than the specific combinations recited for the claim dependency.Modifications may also be made to the embodiments hereinbefore describedwithout departing from the scope of the present technique. For instance,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognise thatvarious features of the described embodiments may be combined inaccordance with this disclosure.

The following numbered clauses provide further aspects and examples ofthe present disclosure:

1. A user device for transmitting and receiving data to and from aninfrastructure equipment via a wireless access interface, the userdevice configured

to receive an indication from the infrastructure equipment of a locationand duration of a temporal response window for receiving responsemessages, the response messages being received in response to accessrequest messages and the location and duration of the temporal responsewindow having been determined by the infrastructure equipment,

to transmit an access request message for requesting access to thewireless access interface to the infrastructure equipment, and

to receive a response message in response to the access request messagefrom the infrastructure equipment, wherein

the user device is configured to receive the response message in thetemporal response window.

2. A user device according to clause 1, wherein the user device isconfigured to receive the response message in one or more of a pluralityof temporal response windows, the plurality of response windowsseparated in time, a location and duration of the temporal responsewindows having been determined by the infrastructure equipment and theuser device having received an indication of a location and duration ofat least one of the response windows from the infrastructure equipment.

3. A user device according to clauses 1 or 2, wherein the user device isconfigured to transmit the access request message to the infrastructureequipment via one or more relay nodes.

4. A user device according to clauses 2 or 3, wherein the indication ofa location and duration of at least one of the response windows isreceived by the user device from the infrastructure equipment prior tothe transmission of the access request message.

5. A user device according to any of clauses 2 to 4, wherein the userdevice is configured to enter a reduced power state during the timeseparating the response windows.

6. A user device according to any of clauses 2 to 5, wherein the userdevice is configured is configured to receive the indication of alocation and duration of at least one of the response windows from theinfrastructure equipment in one of the response windows.

7. A user device according to any of clauses 2 to 6, wherein the userdevice has an identifier associated therewith and the infrastructureequipment is configured to determine the location and duration of atleast one of the response windows based upon the identifier of the userdevice and a predetermined rule, and the user device is configured todetermine the location and duration of the at least one of the responsewindows based on the identifier associated therewith and thepredetermined rule.

8. A user device according to any preceding clause, wherein the userdevice is a 3GPP LTE compliant device.

9. A user device according to any preceding clause, wherein the accessrequest message includes a random access preamble and the responsemessage is a random access response.

10. A method for transmitting and receiving data from and to a userdevice to and from an infrastructure equipment via a wireless accessinterface, the method comprising

receiving an indication from the infrastructure equipment of a locationand duration of a temporal response window for receiving responsemessages, the response messages being received in response to accessrequest messages and the location and duration of the temporal responsewindow having been determined by the infrastructure equipment,

transmitting an access request message for requesting access to thewireless access interface to the infrastructure equipment from the userdevice, and

receiving a response message in response to the access request messagefrom the infrastructure equipment at the user device, wherein the methodcomprises

receiving the response message at the user device in the temporalresponse window.

11. A user device for transmitting and receiving data to and from aninfrastructure equipment via a wireless access interface, the userdevice configured

to transmit an access request message for requesting access to thewireless access interface to the infrastructure equipment, and

to receive a response message in response to the access request messagefrom the infrastructure equipment, wherein

the user device is configured to receive the response message within oneor more of a plurality of temporal response windows, the plurality ofresponse windows separated in time and the user device having beenprovided with an indication of the location and duration of at least oneof the plurality of temporal response windows.

12. A user device according to clause 11, wherein the user device isconfigured to transmit the access request message to the infrastructureequipment via one or more relay nodes.

13. A user device according to clauses 11 or 12, wherein the user deviceis configured to enter a reduced power state during the time separatingthe response windows.

14. A user device according to any of clauses 11 to 13, wherein theaccess request message includes a random access preamble and theresponse message is a random access response.

The invention claimed is:
 1. A wireless user device comprising:circuitry configured to: receive a duration of a temporal responsewindow from an infrastructure equipment; transmit an access requestmessage for requesting access to the infrastructure equipment over arelay path, the relay path including a plurality of nodes used to relaythe access request message from the wireless user device to theinfrastructure equipment; in response to the access request message,receive a response message within the duration of the temporal responsewindow from the infrastructure equipment; receive the response messagein one or more of a plurality of temporal response windows, theplurality of temporal response windows separated in time, durations ofthe temporal response windows having been determined by theinfrastructure equipment; and receive a duration of at least one of thetemporal response windows from the infrastructure equipment.
 2. Thewireless user device according to claim 1, wherein the circuitry isfurther configured to receive the duration of at least one of thetemporal response windows from the infrastructure equipment prior to thetransmission of the access request message.
 3. The wireless user deviceaccording to claim 1, wherein the circuitry is further configured toenter a reduced power state during the time separating the temporalresponse windows.
 4. The wireless user device according to claim 1,wherein the circuitry is further configured to receive the duration ofat least one of the temporal response windows from the infrastructureequipment in one of the temporal response windows.
 5. The wireless userdevice according to claim 1, wherein the circuitry is further configuredto determine the duration of the at least one of the temporal responsewindows based on an identifier of the wireless user device and apredetermined rule.
 6. The wireless user device according to claim 5,wherein the circuitry is further configured to receive the duration ofat least one of the temporal response windows from the infrastructureequipment that determines the duration of at least one of the temporalresponse windows based upon the identifier of the wireless user deviceand the predetermined rule.
 7. The wireless user device according toclaim 1, wherein the wireless user device is a 3GPP LTE compliantdevice.
 8. The wireless user device according to claim 1, wherein theaccess request message includes a random access preamble and theresponse message is a random access response.
 9. A method for a wirelessuser device, the method comprising: receiving a duration of a temporalresponse window from an infrastructure equipment; transmitting an accessrequest message for requesting access to the infrastructure equipmentover a relay path, the relay path including a plurality of nodes used torelay the access request message from the wireless user device to theinfrastructure equipment; in response to the access request message,receiving a response message within the duration of the temporalresponse window from the infrastructure equipment; receiving theresponse message in one or more of a plurality of temporal responsewindows, the plurality of temporal response windows separated in time,durations of the temporal response windows having been determined by theinfrastructure equipment; and receiving a duration of at least one ofthe temporal response windows from the infrastructure equipment.
 10. Themethod according to claim 9, the method further comprising: receivingthe duration of at least one of the temporal response windows from theinfrastructure equipment prior to the transmission of the access requestmessage.
 11. The method according to claim 9, the method furthercomprising: entering a reduced power state during the time separatingthe temporal response windows.
 12. The method according to claim 9, themethod further comprising: receiving the duration of at least one of thetemporal response windows from the infrastructure equipment in one ofthe temporal response windows.
 13. The method according to claim 9, themethod further comprising: determining the duration of the at least oneof the temporal response windows based on an identifier of the wirelessuser device and a predetermined rule.
 14. The method according to claim13, the method further comprising: receiving the duration of at leastone of the temporal response windows from the infrastructure equipmentthat determines the duration of at least one of the temporal responsewindows based upon the identifier of the wireless user device and thepredetermined rule.
 15. The method according to claim 9, the methodfurther comprising: transmitting and receiving data to and from thewireless user device according to a 3GPP LTE protocol.
 16. The methodaccording to claim 9, the method further comprising: transmitting theaccess request message including a random access preamble for requestingaccess to the infrastructure equipment; and receiving the responsemessage, which is a random access response, within the duration of thetemporal response window from the infrastructure equipment.